Cargo containers are well known, and are typically transported by ships, trains, and trucks. Containers may also be transported by air, and certain containers have been specially shaped to fit into the curved hulls of airplanes. In most instances it is desirable to reduce the weight of the cargo container to conserve fuel and, in some applications, increase the weight of the cargo that may be carried. For example, Federal Truck Size and Weight limitations restrict gross vehicle weight to less than 80,000 pounds on the U.S. Interstate system. If the weight of the container can be decreased, the maximum transportable cargo weight is increased. Thus, it is desirable to have a cargo container with a minimal weight so that cargo weight can be maximized.
The use of polymer materials in lieu of metal components in container construction can reduce the total weight of the container. However, polymers may fracture when a force is exerted upon the material. Fractures in polymers cannot usually be repaired as easily as dents in metal, and complete replacement of the fractured polymer is often required. Thus, it is desirable to minimize the size of complete polymer sections so that, if replacement becomes necessary, the amount of material being replaced is minimized when repair is required.
The complexity of panel joints often results in structural weakness due to a greater likelihood of a defective or improperly assembled portion. In contrast, panel fabrication is commonly a simpler, more automated process producing a product of more consistent quality. Joints that utilize multiple materials, such as bolts and clips, are further subjected to increased corrosion, uneven wear, and uneven thermal expansion and contraction. Also, since joints are typically at the very ends of panels, forces acting upon a jointed panel will commonly exert the greatest torque at the joint.
Cargo container joints often require significant reinforcement so that the joint can withstand the compressive and tension load exerted upon them. Joint reinforcement increases the total weight of the container, often reducing the amount of cargo that can be legally carried. The size of the joint reinforcements may even reduce the total cargo volume carryable. Cargo containers with rounded edges have the advantage of providing a substantially continuous load path where the force of the load is substantially spread between the vertical and horizontal portions of the container. Even if the amount of cargo is not limited by the reinforcements, the additional weight will often increase the cost of transporting the container.
Cargo containers and panels wear out with time and must eventually be replaced, thus it is desirable to have a cargo container that is easily manufactured with small replaceable panels. Additionally, expensive machinery is often required to produce large polymer panels while smaller pieces can be produced by smaller, cheaper, machinery. Also, the use of a segmented cargo container allows for the parallel production of several components at once.
There are many problems associated with cargo container joints, joint reinforcement, container construction, and the forces exerted upon the edges of cargo containers. Thus, it is desirable to have a cargo container with rounded edges made from a plurality of panels where the panel joints and rounded edges of the container are spatially separated.
There have been attempts to solve these problems, however none have yielded a solution capable of solving all of the disclosed problems. For example, U.S. Pat. No. 5,289,933 that issued to Streich et al. discloses a collapsible cargo container that is jointed together in the corner regions of the container. The '933 patent fails to disclose the use of highly curved panels capable of distributing torsional forces over a large area of the joint.
U.S. Pat. No. 4,214,669 that issued to McQuiston discloses a collapsible cargo container with joints that are not located at the edges of the container. As with the '933 patent, the '669 patent fails to disclose rounded edges, and shows reinforced corners.
U.S. Pat. No. 5,690,378 issued to Romesburg discloses a monocoque cargo container that with a top and bottom piece jointed together. The '378 patent, however, fails to disclose the use of many separate panels in the construction of the cargo container. Such a design is not easily manufacturable or repairable due to the use of very large component pieces.
U.S. Pat. Nos. 5,041,318, 5,472,290, and 6,095,715 that issued to Hulls disclosed the use of joints between the top and side of a cargo container that provide “a substantially continuous load path.” The Hulls patents disclose the advantages of a cargo container with curved edges, but fail to disclose a joint that is distant from the cargo container edges. The Hulls patents also do not disclose the use of multiple individual panels that can be easily manufactured or replaced when damaged.